Xen users - Mar 2007 - file-backed vs. block device performance

Hi,

I searched the archives and I couldn''t find a thread with specific
metrics
or benchmark results for file-backed VBD vs. raw disk partitions. Does
anyone know any good links?

mark


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Hi again,

Since I''ve not heard anything I''m assuming that no metrics
exist, right?
Would it be appropriate to do a small test? Is anyone interested?

I was thinking of setting up and file-backed and partition-backed domain and
running lmbench to do some simple benchmarking -- does this sound
appropriate?

mark

On 3/27/07, Mark Greenbank <mark.greenbank@gmail.com>
wrote:
>
> Hi,
>
> I searched the archives and I couldn''t find a thread with specific
metrics
> or benchmark results for file-backed VBD vs. raw disk partitions. Does
> anyone know any good links?
>
> mark
>
>

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http://lists.xensource.com/xen-users

Mark Greenbank wrote:
> Hi again,
> 
> Since I''ve not heard anything I''m assuming that no
metrics exist, right?
> Would it be appropriate to do a small test? Is anyone interested?
> 
> I was thinking of setting up and file-backed and partition-backed domain 
> and running lmbench to do some simple benchmarking -- does this sound 
> appropriate?
Hi Mark,
I''ve done some (basic) fs benchmarking on our setup:
- Sles10/Xen 3.0.2
- Xeon 5130 - 2Ghz
- 4 GB ram
- Disk: 1.2TB on Areca raid controller 1130 on raid6
- FS: xfs for xen VMs

Benchmark done using lmdd, command like:
Write) lmdd.linux of=... bs=1024k count=1000 fsync=1
and
Read)  lmdd.linux if=... bs=1024k count=1000 fsync=1
Commands are repeated at least 5 times to ensure no cache influence.

Here are some results:
VM has physical access to a logical volume
  * write -> 209 MB/s
  * read  -> 299 MB/s
I''ve done some tests using file images, too. Results where around 15 
MB/s (write) and 18 MB/s (read), If I remember correctly...
If interested I can give you more details.

With respect to native performance we have that the single VM was able
to reach the following % of native speed:
- write: 92%
- read : 88%
This was not intended to be a comprehensive test suite, but only to look
at some numbers wrt physical device utilization.

Regards,
-- 
-- Marco Mililotti
"Democracy is two wolves and a lamb voting on what to have for lunch.
Liberty is a well-armed lamb contesting the vote."
Benjamin Franklin

-- 
-- Marco Mililotti
"Democracy is two wolves and a lamb voting on what to have for lunch.
Liberty is a well-armed lamb contesting the vote."
Benjamin Franklin

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Hi,

I did some tests last year that may help you out. Look for an email
titled "Differences in performance between file and LVM based images",
sent on 08/24/2006.

Cheers,
Alex     

Mark Greenbank wrote:
> Hi,
>
> I searched the archives and I couldn''t find a thread with specific
> metrics or benchmark results for file-backed VBD vs. raw disk
> partitions. Does anyone know any good links?
>
> mark
>
> ------------------------------------------------------------------------
>
> _______________________________________________
> Xen-users mailing list
> Xen-users@lists.xensource.com
> http://lists.xensource.com/xen-users



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